CAUDAL AUTOTOMY AND REGENERATION IN THE GECKO 177% 
skin and subcutaneous fat layer in this region are unsegmented. 
The submuscular fat bands are absent, their position and that 
of the muscles of the tail segments being occupied by large 
longitudinally-disposed masses of muscle doubtless concerned 
with the occasional movements of the tail base. The type of 
muscles found in the segments of the tail is quite absent. 
In the base, i.e. the region between the cloacal aperture and 
the first autotomy plane (marking the anterior border of the 
first seement), two and a half vertebrae are to be found in the 
adult, Gecko (I found three and a half. vertebrae in the base of 
a young Gecko), and the base thus consists of the equivalents of 
two and a half tailsegments. Only two haemal arches are present 
in the region of the base, these being attached to the last two 
intercentral cartilages, the first intercentral cartilage only pos- 
sessing, like the trunk vertebrae, a small ventral nodule of bone. 
Tur CaupaL Furxor MusciuEs: THEIR ATTACHMENTS AND 
Mops or AcTION IN AUTOTOMY. 
If we catch a Gecko by its original tail and examine the 
front aspect of the piece shed, we see (Text-fig. 38, A) that 
lying external to and arising from the four submuscular fat 
bands are eight projecting muscle processes (numbered 2’ 2”, 
4’ 4”, 6’ 6”, 8’ 8” on each side of the segment), two arising from 
each fat band. If we examine the hind aspect of the portion 
of tail left attached to the animal (Text-fig. 3,.B) we again see 
the four fat bands, external to which are eight cavities which, 
before autotomy, lodged the eight muscle processes just 
mentioned ; there are also to be seen two pairs of small tapering 
muscle extremities, one in the mid-dorsal line (labelled 1’) 
and one in the mid-ventral line (labelled 10’). The transverse 
processes of the vertebra are also conspicuous. If we now 
remove from a single shed segment of the tail the skin and the 
subcutaneous fat layer, the entire musculature of the segment 
becomes visible (Text-fig. 8, C). Anteriorly the eight muscle 
processes are to be seen; posteriorly each of the four dorsal 
processes is seen to bifurcate, the halves of each, however, 
unitmg with adjacent halves, except in the case of the two 
